This invention relates to a clean transfer method and an apparatus therefor, and more particularly to a clean transfer method for transferring objects to be transferred (hereinafter referred to as "transferred objects") required for processing and/or assembling a product associated with a semiconductor, an optical disc or the like while keeping an operating environment clean and free of any contamination, and an apparatus therefor.
The assignee proposed transfer of an optical mini-disc or a product associated with a semiconductor such as a semiconductor wafer or the like between vacuum units by means of a vacuum clean box for the transportation during the manufacturing, as disclosed in U.S. patent application Ser. No. 08/176,197 filed on Jan. 3, 1994.
FIGS. 8A to 9B show a procedure for transfer of transferred objects between vacuum units by means of a vacuum clean box as described above, wherein reference numeral 10 designates a vacuum clean box and 12 is a vacuum unit. The vacuum clean box 10 includes a box body 14 provided at one or a lower end thereof with a first opening 16 and a first shutter 18 acting also as a lid and arranged for selectively airtightly closing the opening 16. The vacuum clean box 10 is constructed so as to be kept a vacuum therein due to closing of the box body 14 by the first shutter 18, to thereby eliminate arrangement of any vacuum evacuation means and transfer means in the vacuum clean box 10. The first shutter 18 is mounted on an front or upper surface thereof with a holder 20 for supporting transferred objects such as optical mini-discs, products associated with a semiconductor or the like thereon. Also, the first shutter 18 is formed on a rear or lower surface thereof with a plurality of aligning recesses 22, in which positioning pins 24 provided on a side of the vacuum unit 12 which will be described hereinafter are detachably fitted, respectively.
The vacuum unit 12 is attached to a vacuum processing apparatus in order to transfer the transferred objects such as optical mini-discs, products associated with a semiconductor or the like by means of the vacuum clean box 10. For this purpose, the vacuum unit 12 includes a vacuum evacuation means, as well as an airtight vessel 26 provided with a second opening 28, a second shutter 30 mounted on a distal end of an actuation rod 32, a spacer block 34 fixed on an upper surface of the second shutter 30 and a plurality of the above-described positioning pins 24 fixed on the spacer block 34 so as to upwardly extend from an upper surface thereof. The shutter actuation rod 32 is constructed so as to be extendably actuated in order to vertically move the shutter 30. The positioning pins 24 are detachably fitted in the aligning recesses 22 of the first shutter 18 on the side of the vacuum clean box 10. The second opening 28 is defined by a connection block 38 fixed on the airtight vessel 26.
In the conventional clean transfer apparatus of FIGS. 8A to 9B thus constructed, when the vacuum clean box 10 is not placed on the vacuum unit 12 as shown in FIG. 8A, the second opening 28 of the vacuum unit 12 is closed by the second shutter 30 and an outer surface of the second shutter 30 is exposed to an ambient atmosphere. When the transferred objects in the vacuum clean box 10 is to be moved to the vacuum unit 12, the vacuum clean box 10 is placed on the opening 28 of the vacuum unit 12, as shown in FIG. 8B. Concurrently, the positioning pins 24 are fittedly inserted in the aligning recesses 22 of the vacuum clean box 10. This results in the vacuum clean box 10 being connected to the vacuum unit 12, so that the connection block 38, first shutter 18 and second shutter 30 cooperate with each other to define an intermediate area 40 acting as a closed space. The intermediate area 40 is initially exposed to an atmospheric pressure and then evacuated through a vacuum evacuation path 42 by means of a vacuum evacuation means (not shown) on the side of the vacuum unit 12, so that a high vacuum is formed therein.
Such evacuation of the intermediate area 40 to a vacuum causes a difference in pressure between an outside of the shutter 18 of the vacuum clean box 10 and its inside to be eliminated; so that contraction of the actuation rod 32 of the vacuum unit 12 and downward movement of the shutter 30 and spacer block 34 cause the shutter 18 and holder 20 on which the transferred objects are held to be concurrently downwardly moved together with the second shutter 30 and spacer block 34 as shown in FIG. 9A, because a weight of the shutter 18 and that of the transferred objects held on the holder 22 act thereon. This results in a space in the vacuum unit 12 communicating with a space in the vacuum clean box 10, so that the shutter 18 and transferred objects may be introduced into the airtight vessel 26.
When the vacuum clean box 10 connected to the vacuum unit 12 as described above is to be released from the vacuum clean box 10, the actuation rod 32 is expanded to cause the intermediate area 40 formed by cooperation of the connection block 38, first shutter 18 and second shutter 30 with each other to be airtight. Then, the intermediate area 40 is returned to an atmospheric pressure, so that the atmospheric pressure in the intermediate area 40 acts on a lower surface of the first shutter 18, resulting in the box body 14 and first shutter 18 being sealedly joined to each other. This permits the first shutter 18 to be smoothly released or disengaged from the positioning pins 24. Then, the box body 14 and first shutter 18 are integrally joined to each other in an airtight manner, to thereby provide the vacuum clean box 10 having the transferred objects received therein, which is then transferred to any desired location.
As noted from the above, in the conventional clean transfer apparatus, the first shutter 18 of the vacuum clean box 10 and the second shutter 30 of the vacuum unit 12 are concurrently operated. Unfortunately, such concurrent operation fails to permit a unit operated under an atmospheric pressure to be substituted for the vacuum unit 12. More particularly, even when the intermediate area 40 which has been rendered airtight is evacuated to a vacuum, an air atmosphere enters the intermediate area 40 when concurrent opening of the shutters 18 and 30 is started, leading to a failure in opening of the shutter 18. Thus, the conventional clean transfer apparatus shown in FIGS. 8A to 9B is restricted to only transfer of the transferred objects between the vacuum units by means of the vacuum clean box 10. Unfortunately, manufacturing of a semiconductor or the like is restricted to a substantially narrowed range, so that a range of vacuum clean transfer applied to the manufacturing is restricted correspondingly.
Also, the construction of the conventional clean transfer apparatus wherein the first shutter 18 of the vacuum clean box 10 and the second shutter 30 of the vacuum unit 12 are concurrently operated causes a difference between a pressure in the vacuum clean box 10 and that in the vacuum unit 12 to be substantially increased, when the vacuum clean box 10 is kept non-operated for a long period of time, to thereby be decreased in vacuum. This leads to a problem of causing dust to be scattered in the vacuum clean box 10 and vacuum unit 12 when both communicate with each other.